1. Field
This application is generally related to an optical gyroscope apparatus and a system employing an optical gyroscope apparatus. The application is also related to a method for observing sensitivity of an optical gyroscope.
2. Related Art
Over the last decade, efforts have been made to improve the sensitivity of optical gyroscopes. Gyroscopes are devices for measuring rotation rates or changes in angular velocity about an axis of rotation. Rotation about the axis normal to the waveguide either slows or speeds the propagation of light through the waveguide, resulting in a measurable shift in phase of the light. Namely, a loop of the optical waveguide is employed in view of principles of the Sagnac effect to measure the interference of counter-propagating waves therein. Interference is affected when the plane of the loop is tilted. That is, one wave “experiences” a shorter optical path thereby changing the interference with the other wave.
The sensitivity of an interferometric gyroscope depends upon its length L and loop diameter D as described in equation (1) below. Namely large L and D values directly improve performance by reducing the minimum detectable change in angular rotation δΩ. An interferometric gyroscope is operated with a source at center wavelength λ0 and power P of photon energy hν that is detected by a photodetector with quantum efficiency h and integration time t.
                    δΩ        =                                            c              ⁢                                                          ⁢                              λ                0                                                    2              ⁢              LD                                ⁢                                    (                              hv                                  P                  ⁢                                                                          ⁢                  ητ                                            )                                      1              /              2                                ⁢                                          ⁢          in          ⁢                                          ⁢          rad          ⁢                      /                    ⁢          s                                    (        1        )            
In view of equation (1), conventional gyroscopes have lengths tens of meters in length to reduce angular rotation. This length may even extend in excess of 1 kilometer based upon the desired sensitivity of the gyroscope. Accordingly, conventional gyroscopes tend to be bulky and expensive.
Generally, optical waveguides in photonic integrated circuits (PICs) are fabricated by lithographically patterning a substrate upon which one or more optical components are integrated. The substrate is generally made of silicon and may include a silica layer formed through thermal or native oxidation. However, silicon and silicon dioxide waveguides exhibit very high background losses of about 1 dB/cm. In practice, this limits the sensitivity of the gyroscope device.
What is desired in the art is a waveguide-based gyroscope apparatus exhibiting improved sensitivity characteristics.
What is also desired in the art is a waveguide-based gyroscope that is compact.
What is further desired in the art is a waveguide-based gyroscope that is inexpensive to commercially manufacture.